XANA is a code, named after the program, XANA. When the XANA code is entered into a Tower it gives Xana complete control over the sector the tower is in. When it was used in the third season Xana used the code to delete the sectors of Lyoko to prevent the Lyoko Warriors from accessing Carthage.
Known Uses for Code: XANAEdit
This was the first function of the code that is seen in the series. XANA would use the Scyphozoa to possess Aelita and guide her to the Way Tower of the sector she was in (as this tower held all codes that upheld the sector). Once she had entered the code into the tower interface, XANA would have full access to the sector and using this power he would delete the sector entirely. The main purpose of destroying the sectors was to prevent Team Lyoko from accessing Carthage with the Transport Orb. Aelita destroyed the Forest first in Lyoko Minus One, the Desert in The Pretender, she willing used the code to save the supercomputer by destroying the Ice Barrier in Sabotage and finally destroying the Mountains in Double Trouble.
Tower Activation Edit
Another function of code is the ability to instantly activate a tower for XANA. In the series, XANA could only activate neutral towers instantly however if he attempted to take control of others, he usually met strong resistance. The first and only use of this function was displayed when William used it in the missed episode Lab Rat to deteleport Odd and Aelita. William performs the same proscedure that Aelita does to deactivate a tower: first he enters the tower, levitates to the top, and enters Code: XANA on the interface, deteleporting everyone back into the Skid.